Raphael -josia



I UNITED STATES PATENT @FFTCE.

RAPHAEL JOSIA, OF FLORENCE, ITALY, ASSIGNOR TO WVILLIAM REY AND C. DE VARIGNY, BOTH OF PARIS, FRANCE.

COMPOSITION FOR TREATING SULPHATES OF LIME FOR THE MANUFACTURE OF ARTIFICIAL MARBLE.

SPECIFICATION forming part of Letters Patent No. 265,512, dated October 3, 1882.

Application filed August 9, 1892.

To all whom it may concern.-

Be it known that I, RAPHAEL Jos1A,ofFlorence, Kingdom of Italy, have invented or discovered a new and useful Improvementin 0on1- positions for Treating Sulphates of Lime for the Manufacture of Artificial Marble; and I do hereby declare the following to be a full, clear, concise, and exact description thereof.

In an application for Letters Patent of the United States filed March 2, 1882, I have described and made claim to an improved process of treating or preparing gypsum (calcic sulphate or sulphate of lime) in the making of articles of a material which I have termed certaldite without pulverization of the gypsum. In said application I described briefly certain ot'the compounds orcompositions which I employ to produce certain effects and the manner of using them, but stated that separate applications would be made for patents for such compositions.

The present application relates to one of the compositions so referred to, and itis designed for use in the process herein described in the making of sky-blue certaldite.

In carrying out the process referred to a suitable piece of gypsum (calcic sulphate) is first formed into the desired shape, or approximately such, by the use of suitable well-known tools. The gypsum employed may be the ordinary native gypsum of commerce, though I prefer that which is comparatively pure or free from other matters of different composition. Such gypsum is usually obtained hydrated, or containing a certain percentage of water in its composition; and the second step in the operation has reference to depriving the gypsum under treatment of a considerable part or the whole ofsuch water. Thisis done bysubjecting it to the action of a gradually-increasing heat, varying by preference with the size and quality of the material from 260 to 300 Fahrenheit, for about twelve hours, or until the desired partial or complete dehydration is obtained. The length of time as well as the degree of heat required to effect this result will vary somewhat with the size, character, and purity of the gypsum employed; But the temperature should-not exceed 500 Fahrenheit, and both it and the time of exposure should be regulated and limited with reference to securing uniformity of (No specimens.)

treatment throughout the whole mass or bod'v. This operation may be known to be complete when the fracture of a test block presents a uniform white color. Any suitable drying or baking apparatus may be employed for this purpose, many such being known in kindred branches of the arts; but it should be of such construction that the material undertreatment shall not be brought into direct contact with the. tire. \Vhen the desired dehydration has been effected the furnace is allowed to cool gradually, in order thatthe material under treatment may be cooled gradually; or the material may be removed with due care to prevent breaking ard exposure to moisture. and

allowed to cool outside the furnace gradually u'n til it is reduced in temperature sufficiently to permit handling with safety in its subsequent treatment, which is designed to impart to it the desired color or tint and a high degree of insolubility and hardness throughout its mass. This step involves the use of the composition which lorms the subject-matter of invention in the present application. This compositionistormedot'thet'ollowingelements: Water, by weight, two hundred parts; oxalic acid, by weight, two to two and one-halt'parts; alum, by weight, ten to eleven parts; cyanide of potassium, by weight, fifteen one thousandth to three one-hundredth parts. These ingredients, being mixed in about the proportions named, form a solution whichis used as a bath, and to this end a suitable quantity of it is placed in a vessel of proper shape to receive the article to be treated,which is dipped or immersed in the bath and subjected to its action until the article has acquired the desired degree ofha-rdness and color. Thelength of time required to effect this result will depend somewhat on the strength of the ingredients composing the bath or solution, the porosity and nature or physical and chemical condition of the article; but usually twelve hours (more or less) will suffice, though to secure uniformity of treatment and ofresult through the whole body or mass of the article I prefer repeated dippings-two, three, or more-say two or three seconds at first, and increasing gradually to one, two,three,or more minutes, more or less, with drying intervals of like increasing length between clippings, for

half or three-quarters of an hour or so, after which the article may remain in the bath for twelve hours or so.

\Vhile I do not limit my invention by any particular theory of chemical or physical reactions involved in the use of this bath as above described, I believe, with my present knowledge, thatthe salt (alum) held in solution, by taking the place of the molecules of water displaced by the previous dehydrating operation, acts chemically or physically upon the calcic sulphate and renders it more compact, harder, and less soluble, and that the oxalic acid of the bath acts chemically or physically upon the impurities or matters of other composition, (carbonates, &c.,) which are usually contained in greater or less quantities in native gypsums, and produces a like indurating effect upon them, though the salt may also have an induratingact-ion upon the impurities present, and the acid may act in like manner more or less upon the calcic sulphate. The alum is also designed in part as a coloring agent. Commercial alum usually contains a small percentage of iron, and this iron, combining with the cyanide of potassium, gives the desired sky-blue color to the calcic sulphate, which will usually be variegated more or less, however, by lines, veins, and markings of irregular form and of darker shades and somewhat different tints of color, produced probably by the impurities present in the gypsum. til'ul appearance is thus given to the article, (certaldite,) as well as such a degree of hardness, insolubility, and susceptibility of taking a high polish as renders it an excellent and valuable substitute for marble, ornamental stones, and tiles in the various uses to which they are applied in the arts.

\Vhen the article has been treated in the bath as above described it is removed and dried by exposure to the sun or to an equivalentfurnace-heatt'oroueortwohours,or byordinary atmospheric exposure for two or three days, when it is ready for polishing and such other manipulation as may best tit it for its intended use, which may be done by any of the methods practiced in kindred arts.

A highly-ornamental and heau-' No claim is made hereinto the process set forth, as that, with various modifications of the same, as circumstances may require, forms the subject-matterof the first application herein referred to. Neither do I limit my present invention to the particular way herein described of applying it, though I now believe this way or process to be the best. I also believe the proportions of ingredients which 1 have named in forming my improved composition to be the best for the purposes stated, and, among others, to secure a uniform degree of hardness and color throughout the mass of the article. If the solution be very strong, there is great danger of rendering the surface of the article hard very quickly, and thereby preventing proper action of the bath upon the interior substance of the article; or if the solution be very weak too much time is required, and even then a proper degree of hardness, density, and insolubility is not secured; also, by the conjoint action of all the elements of the bath much better results are secured, especially upon native gypsums, than by a solution formed of a part of the elements. For these reasons I prefer to employ all the elements of the composition in substantially the proportions named; but such limits, though ati'ording the best results, may be varied or exceeded somewhat and still obtain favorable results under skillful manipulation, and all such modificationsemploying the elements substantially as herein described in about the proportions set forth I consider as coming Within my invention and claim.

I claim as my invention- The composition herein described for treating dehydrated gypsum, consisting substantially ot' the following elements: water, oxalic acid, alum, and cyanide of potassium in about the proportions set forth.

In testimony whereofI have hereunto set my hand.

RAPHAEL JOSIA.

Witnesses Gumo PANTALIONY, It. H. W HIT'ILESEY. 

